Allow custom methods in Rtsp Options response public header

ExoPlayer will not fail playback if an RTSP server responds to the Options request with an unknown RTSP method request type. ExoPlayer will parse the response and just not call methods it does not know how to use.

Issue: androidx/media#613
PiperOrigin-RevId: 568152076

library/rtsp/src/main/java/com/google/android/exoplayer2/source/rtsp/RtspMessageUtil.java

@@ -291,7 +291,8 @@ public static String toMethodString(@RtspRequest.Method int method) {
       case "TEARDOWN":
         return METHOD_TEARDOWN;
       default:
-        throw new IllegalArgumentException();
+        // Return METHOD_UNSET for unknown Rtsp Request method.
+        return METHOD_UNSET;
     }
   }
 
@@ -394,7 +395,10 @@ public static ImmutableList<Integer> parsePublicHeader(@Nullable String publicHe
 
     ImmutableList.Builder<Integer> methodListBuilder = new ImmutableList.Builder<>();
     for (String method : Util.split(publicHeader, ",\\s?")) {
-      methodListBuilder.add(parseMethodString(method));
+      @RtspRequest.Method int rtspRequestMethod = parseMethodString(method);
+      if (rtspRequestMethod != METHOD_UNSET) {
+        methodListBuilder.add(rtspRequestMethod);
+      }
     }
     return methodListBuilder.build();
   }